Magnetic resonance imaging (MRI) is a non-invasive imaging technique that employs a powerful magnet to align the nuclei of atoms inside a target body, and a variable magnetic field that causes the atoms to resonate, a phenomenon called nuclear magnetic resonance. MRI may generate images with high resolution on soft tissues including, for example, urinary bladder, rectum, uterus, bone, articulation, muscle, etc. Positron emission tomography (PET) is a functional imaging technique that detects pairs of gamma rays emitted by a positron emitting radionuclide or a tracer. PET may be adopted to investigate metabolic process of a target body and used widely in field including, for example, oncology, neurology, psychiatry, cardiology, infectious diseases, musculo-skeletal imaging, etc. Positron emission tomography-magnetic resonance imaging (PET-MRI) is a hybrid imaging technique that utilizes the benefits of both PET and MRI. However, radio-frequency coils used for MRI process may cause attenuation of gamma rays in PET process.